Suspension with hydraulic preload adjust

ABSTRACT

A shock absorber for a vehicle having a damper and a first and second springs mounted coaxially around the damper and a preload adjuster for partially compressing at least one of the springs independently of the compression stroke. In one embodiment the preload adjuster is remotely controllable. In another embodiment the shock absorber includes an additional mechanism for preloading at least one of the springs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a continuation of theco-pending patent application, Ser. No. 14/293,927, Attorney DocketNumber FOX-0062US.CON entitled “SUSPENSION WITH HYDRAULIC PRELOADADJUST,” with filing date Jun. 2, 2014, by Christopher Paul Cox, whichis incorporated herein, in its entirety, by reference.

The application with Ser. No. 14/293,927 claims priority to and is acontinuation of the patent application, Ser. No. 13/758,330 and nowissued U.S. Pat. No. 8,770,592, Attorney Docket Number FOXF/0062USentitled “SUSPENSION WITH HYDRAULIC PRELOAD ADJUST,” with filing dateFeb. 4, 2013, by Christopher Paul Cox, which is incorporated herein, inits entirety, by reference.

The application with Ser. No. 13/758,330 claims priority to the patentapplication, Ser. No. 61/594,886, Attorney Docket Number FOXF/0062USLentitled “SUSPENSION WITH HYDRAULIC PRELOAD ADJUST,” with filing dateFeb. 3, 2012, by Christopher Paul Cox, which is incorporated herein, inits entirety, by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to a damper assembly for avehicle. More specifically, certain embodiments relate to spring preloadadjustment used in conjunction with a vehicle suspension.

2. Description of the Related Art

Vehicle suspension systems typically include a spring component orcomponents and a damping component or components. Typically, mechanicalsprings, like helical springs, are used with some type of viscousfluid-based damping mechanism and the two are mounted functionally inparallel. In some instances, features of the damper or spring areuser-adjustable. What is needed is an improved method and apparatus forvarying spring preload characteristics.

SUMMARY OF THE INVENTION

The present invention generally includes a shock absorber for a vehiclehaving a damper and a first and second springs mounted coaxially aroundthe damper and a preload adjuster for partially compressing at least oneof the springs independently of the compression stroke. In oneembodiment the preload adjuster is remotely controllable. In anotherembodiment the shock absorber includes an additional mechanism forpreloading at least one of the springs.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a section view of a shock absorber having two coaxial springs,both of which are pre-loadable.

FIG. 2 is a section view of the shock absorber of FIG. 1 in which thespring members are pre-loaded.

FIG. 3 is a section view of the shock absorber illustrating anindependent way of pre-loading one of the springs relative to eh otherspring.

FIG. 4 is a schematic diagram showing a control arrangement for aremotely operated bypass.

FIG. 5 is a schematic diagram showing another control arrangement for aremotely operated bypass.

DETAILED DESCRIPTION

As used herein, the terms “down,” “up,” “downward,” “upward,” “lower,”“upper” and other directional references are relative and are used forreference only.

FIGS. 1-3 illustrate a shock absorber 100 having damper and springfunctions. In the Figures the shock is shown in its most extended(rebound) position. The damper 100 includes a cylinder 102 with a rod107 and a piston 105 which is sealed in the cylinder with a seal 108. Inone embodiment, as the piston 105 moves in a compression or reboundstroke, fluid meters from one side of the piston 105 to the other sideby passing through flow paths (not shown) formed in the piston 105.Typically, shims are used to partially obstruct flow paths through thepiston 105 in each direction. By selecting shims having certain desiredstiffness characteristics, the dampening effects caused by the piston105 as it travels through the fluid can be increased or decreased, anddampening rates can be different between the compression and reboundstrokes of the piston 105.

A reservoir (not shown) is typically in fluid communication with thedamper cylinder 102 for receiving and supplying damping fluid as thepiston rod 107 moves in and out of the cylinder. The reservoir includesa cylinder portion 128 in fluid communication with the damper cylinder102. Certain features of reservoir type dampers are shown and describedin U.S. Pat. No. 7,374,028, which is incorporated herein, in itsentirety, by reference. One end of the piston rod 107 is supplied withan eyelet 109 for connecting to a portion of a vehicle wheel suspensionlinkage. An opposite end (opposite the piston), is supplied with aneyelet 111 to be mounted to another portion of the vehicle, such as theframe, that moves independently of the first part.

In one embodiment, as shown in all of the figures, a closure 110, isconstructed and arranged to thread onto an end of cylinder 102 andengage telescopically with a preload piston 120. The preload piston isslidable relative to and sealed against (by seal 131) an exteriorsurface of cylinder 102 and is also slidably sealed against an exteriorof the closure 110 by seal 132.

The preload piston includes two separate spring axial abutmentstructures. Shown are large diameter abutment 115 and a small diameterabutment 130. A spring abutment 125 is attached at an opposite end ofrod 107, adjacent a lower connecting eye. As shown in the figures,abutment 125 may be stepped with two surfaces 126, 127 and of sufficientdiameter to support either the lower end of a large diameter spring 150or a small diameter spring 155 or both simultaneously (as shown).

In one embodiment, a preload adjuster assembly includes a hydraulicfluid flow path comprising fill fitting 160, flow path 161, 162 andpiston chamber 163 (visible in FIG. 2). In practice, one or more springsare mounted to abut surfaces 125 and one or both of 115 and 130. FIG. 1shows the shock absorber in the “minimum extension” position (nohydraulic fluid in chamber 163) as it is shown in FIG. 1. The springs150, 155 so mounted will be in their most compliant state due to minimumpreload (i.e. pre-compression). When greater preload and hence morerigid vehicle ride are desired, fluid is introduced manually or viaonboard hydraulic reservoir and pump, into port 160. The fluid thenflows through paths 161, 162 and begins to expand chamber 163. Aschamber 163 expands due to fluid fill (see FIG. 2), the piston 120 movesaxially, compressing spring 150, 155 against abutment 125 (between theabutment 130 and or 115). The result is a stiffer spring.

In the embodiment shown in the Figures, both springs 150, 155 are actedupon by the preload piston 120 causing both to become more or lesscompressed as the preload piston 120 moves in relation to the fluid inchamber 163. However, it will be understood that either of the springscould be independently mounted wherein it is not affected at all by theexpansion and contraction of the chamber 163.

While the embodiment described presumes chamber 163 of the preloadadjuster is operated with relatively non-compressible fluid,compressible fluid such as gas may be used in the chamber to create acomposite spring rate comprising compressible gas and mechanical spring.

While the embodiment described includes springs coaxially arrangedaround a fluid damper, the spring could be used in conjunction with anair spring, especially one that is combined in a central cylinder memberwith a damper. An example of a combination air spring/damper is taughtin U.S. Patent Application Publication No. 2009/0236807 A1 and thatpublication is incorporated herein in its entirety.

In the embodiment shown, large diameter abutment 115 holding largerdiameter spring 150 at one end is independently adjustable relative tothe other spring 155 and the chamber. Independent adjustment is providedby a threaded relationship 156 between the abutment 115 and the outerdiameter of the chamber. For example, in FIGS. 1, 2 the abutment islocated near an end of the chamber wall. In FIG. 3, however, abutment115 has been threadedly moved axially along the cylinder to a locationcloser to an opposite end of the chamber. In this manner, additionalpreload is placed upon the larger diameter spring 150 separate and apartfrom preload supplied by the preload piston 120. While the independentadjustment feature is shown in relation to the larger diameter spring150, it will be understood that such a feature could be associated witheither or both springs. Additionally, any number of springs (including asingle spring) can be used with their ends mounted at various locationsalong a length of the cylinder 102.

The preload adjuster may be automated such that onboard load sensingassociated with a vehicle adjusts the spring rate based on sensedoperational conditions and microprocessor-controlled fluid introductioninto one or more preload adjusters on the vehicle (e.g. 4 on a 4wheeler),

FIG. 4 is a schematic diagram illustrating a sample circuit 400 used toprovide remote control of a preload adjuster using a vehicle's powersteering fluid (although any suitable fluid pressure source may besubstituted for reservoir 410 as could an electrical current source inthe case of an electrically actuated valve member 175). As illustrated,a fluid pathway 405 having a switch-operated valve 402 therein runs froma fluid (or current) reservoir 410 that is kept pressurized by, in oneembodiment, a power steering pump (not shown) to a preload adjuster thatis operable, for example, by a user selectable dash board switch 415.The valve 402 permits fluid to travel to the adjuster, thereby urging itto an expanded position. When the switch 415 is in the “off” position,the adjuster is in its compressed position and no additional preload isplaced on the springs. Hydraulically actuated valving for use withadditional components is shown and described in U.S. Pat. No. 6,073,536and that patent is incorporated by reference herein in its entirety.While FIG. 4 is simplified and involves control of a single preloadadjuster, it will be understood that the valve 402 could be plumbed tosimultaneously provide a signal to two or more adjusters, one related toeach wheel of a vehicle, for instance.

A remotely operable preload adjuster like the one described above isparticularly useful with on/off road vehicles. These vehicles can haveas much as 20″ of shock absorber travel to permit them to negotiaterough, uneven terrain at speed with usable shock absorbing function. Inoff-road applications, compliant shock absorbing is necessary as thevehicle relies on its long travel suspension when encountering off-roadobstacles. However, operating a vehicle with very compliant, long travelsuspension on a smooth road at higher speeds can be problematic due tothe springiness/sponginess of the suspension. Such compliance can causereduced handling characteristics and even loss of control. Such controlissues can be pronounced when cornering at high speed as a compliant,long travel vehicle may tend to roll excessively. Similarly, such avehicle may pitch and yaw excessively during braking and acceleration.With the remotely operated preload adjuster described herein, springcharacteristics of a shock absorber can be completely changed from acompliantly dampened “springy” arrangement to a “stiffer” system idealfor higher speeds on a smooth road.

In addition to, or in lieu of, the simple, switch operated preloadadjuster arrangement of FIG. 4, the preload adjuster can be operatedautomatically based upon one or more driving conditions. FIG. 5 shows aschematic diagram of a remote control system 500 based upon any or allof vehicle speed, damper rod speed, and damper rod position. Oneembodiment of FIG. 5 is designed to automatically increase springcompression in a shock absorber in the event a damper rod reaches acertain velocity in its travel towards the bottom end of travel at apredetermined speed of the vehicle. In one embodiment, the system addsstiffness (and control) in the event of rapid operation (e.g. high rodvelocity) to avoid a bottoming out of the rod as well as a loss ofcontrol that can accompany rapid compression of a shock absorber with arelative long amount of travel. In one embodiment, the system addsstiffness (e.g. expands the chamber 163) in the event that the rodvelocity in compression is relatively low, but the rod progresses past acertain point in the travel. Such configuration aids in stabilizing thevehicle against excessive low rare suspension movement events such ascornering roll, braking and acceleration yaw and pitch and “g-out.”

FIG. 5 illustrates, for example, a system including three variables: rodspeed, rod position and vehicle speed. Any or all of the variables shownmay be considered by processor 502 in controlling the valve 175. Anyother suitable vehicle operation variable may be used in addition to orin lieu of the variables 515, 505, 510 such as, for example, piston rodcompression strain, eyelet strain, vehicle mounted accelerometer data orany other suitable vehicle or component performance data. In oneembodiment, a suitable proximity sensor or linear coil transducer orother electro-magnetic transducer is incorporated in the dampeningcylinder to provide a sensor to monitor the position and or speed of thepiston (and suitable magnetic tag) with respect to the cylinder.

In one embodiment, the magnetic transducer includes a waveguide and amagnet, such as a doughnut (toroidal) magnet that is joined to thecylinder and oriented such that the magnetic field generated by themagnet passes through the piston rod and the waveguide. Electric pulsesare applied to the waveguide from a pulse generator that provides astream of electric pulses, each of which is also provided to a signalprocessing circuit for timing purposes. When the electric pulse isapplied to the waveguide a magnetic field is formed surrounding thewaveguide. Interaction of this field with the magnetic field from themagnet causes a torsional strain wave pulse to be launched in thewaveguide in both directions away from the magnet. A coil assembly andsensing tape is joined to the waveguide. The strain wave causes adynamic effect in the permeability of the sensing tape which is biasedwith a permanent magnetic field by the magnet. The dynamic effect in themagnetic field of the coil assembly due to the strain wave pulse,results in an output signal from the coil assembly that is provided tothe signal processing circuit along signal lines. By comparing the timeof application of a particular electric pulse and a time of return of asonic torsional strain wave pulse back along the waveguide, the signalprocessing circuit can calculate a distance of the magnet from the coilassembly or the relative velocity between the waveguide and the magnet.The signal processing circuit provides an output signal, digital oranalog, proportional to the calculated distance and I or velocity. Sucha transducer-operated arrangement for measuring rod speed and velocityis described in U.S. Pat. No. 5,952,823 and that patent is incorporatedby reference herein in its entirety.

While a transducer assembly measures rod speed and location, a separatewheel speed transducer for sensing the rotational speed of a wheel aboutan axle includes housing fixed to the axle and containing therein, forexample, two permanent magnets. In one embodiment the magnets arearranged such that an elongated pole piece commonly abuts first surfacesof each of the magnets, such surfaces being of like polarity. Twoinductive cons having flux-conductive cores axially passing therethroughabut each of the magnets on second surfaces thereof, the second surfacesof the magnets again being of like polarity with respect to each otherand of opposite polarity with respect to the first surfaces. Wheel speedtransducers are described in U.S. Pat. No. 3,986,118 which isincorporated herein by reference in its entirety.

In one embodiment, as illustrated in FIG. 5, a logic unit 502 withuser-definable settings receives inputs from the rod speed 510 andlocation 505 transducers as well as the wheel speed transducer 515. Thelogic unit is user-programmable and depending on the needs of theoperator, the unit records the variables, and then if certain criteriaare met, the logic circuit sends its own signal to the preload adjusterto either expand or contract. Thereafter, the condition of the preloadadjuster 175 is relayed back to the logic unit 502.

In one embodiment, the logic shown in FIG. 5 assumes a single shockabsorber but the logic circuit is usable with any number of shocks orgroups of shocks. For instance, the shock absorbers on one side of thevehicle can be acted upon while the vehicle's other shocks remainunaffected.

While the examples illustrated relate to manual operation and automatedoperation based upon specific parameters, the remotely operated preloadadjuster can be used in a variety of ways with many different drivingand road variables. In one example, the preload adjuster is controlledbased upon vehicle speed in conjunction with the angular location of thevehicle's steering wheel. In this manner, by sensing the steering wheelturn severity (angle of rotation), additional stiffness can be appliedto one shock or one set of shocks on one side of the vehicle (suitable,for example, to mitigate cornering roll) in the event of a sharp turn ata relatively high speed. In another example, a transducer, such as anaccelerometer, measures other aspects of the vehicle's suspensionsystem, like axle force and/or moments applied to various parts of thevehicle, like steering tie rods, and directs change to the preloadadjuster positioning in response thereto. In another example, thepreload adjuster can be controlled at least in part by a pressuretransducer measuring pressure in a vehicle tire and adding orsubtracting stiffness characteristics to some or all of the wheels inthe event of, for example, an increased or decreased pressure reading.In still another example, a parameter might include a gyroscopicmechanism that monitors vehicle trajectory and identifies a “spin-out”or other loss of control condition and adds and/or reduces springstiffness to some or all of the vehicle's shock absorbers in the eventof a loss of control to help the operator of the vehicle to regaincontrol.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A shock absorber for a vehicle, comprising a fluid-filled damperhaving a piston and rod for movement therein; a first and second springsmounted coaxially around the damper, the springs constructed andarranged to become compressed during a compression stroke of the damper;and a preload adjuster for partially compressing both of the springsindependently of the compression stroke.